Apparatus for metal plating



April 13, 1954 GREENSPAN APPARATUS PoR METAL PLATIN@ 3 Sheets-Sheet lFiled Sept. 16, 1950 April 13, 1954 GREENSPAN 2,575,348

APPARATUS FOR METAL PLATING Filed Sept. 16, 1950 3 Sheets-Sheet 2ATTORNEY April 13, 1954 L.. GREENSPAN APPARATUS FOR .METAL PLATING 5Sheets-Sheet 5 Filed Sept. 16, 1950 FIGB FIG.6

span HT'TORNEY Patented Apr. 13, M1954 UNITED STATES PATENT oEFlcEAPPARATUS Foa METAL PLATTNG Lawrence Greenspan, Bronx, N. Y; Y

Application `September 16, 1950, Serial No. 185,205

8 Claims.

This invention relates to improved devices for rapidly and uniformlyplating objects, and novel methods of plating the objects. Moreparticularly the invention relates to devices for electroformingstampers or dies used in the manufacture of phonograph records andelectrical transcriptions and methods of making said stampers or dies.

It is the general object of the present invention to provide novel andimproved devices and methods for producing stampers rapidly and with aminimum variation in thickness of the electroformed shell or stamperfrom the center to the periphery.

Another object of this invention `is toprovide in a plating apparatus ofthe character described, baie means to direct plating current inwardlyof the periphery of the cathode surface being plated, in order toprevent an excessive build-up of electrodeposited metal at the peripheryand thereby produce a plating of substantially uniform thickness.

A further important objectof this invention is to provide in platingapparatus of the character to be described, means to direct a stream ofgas bubbles through the plating solution and adjacent the cathodesurface being plated, in order to produce vigorous agitation of theplating solution and thereby permit the use of high current densities toobtain rapid plating.

:Still another object of this invention is to provide in a platingapparatus of the character to be described, baiiie'means to direct theplating current uniformly over a metallized cathode surface, and meansto vigorously agitato' the plating solution by passing a flow of airbubbles through the plating solution and adjacent the surface beingplated, whereby high current densities may be employed to decrease theplating time.

Another object of this invention isto provide a device forelectroforming stampers comprising a backplate made of electricallyinsulating ma- 'terial chemically inert to the electrolyte, a cathodeholder attached at one end'to the back o f said backplate, said cathodeholder having its other end adapted to electrically Contact a negativebus bar, and means at the attached end to make electrical contactthrough said back-` jacent to the surface of the object 'to be platedduring the plating process in order to produce vigorous agitation of theelectrolyte over the Whole exposed face of said object and sheet,whereby a high current density may be used to obtain rapid plating.

A further object of this invention is to provide in a device of thecharacter to be described, in clined baffle plates forwardly andinwardly and` scribed, a metal sheet Vinterposed between a chemicallyand electrically inert backplate and the object to be plated, said sheetextending beu yond the edges of said object whereby the plating currentis caused to distribute itself uniformly over the object to be plated,and to elecn trodeposit a shell of substantially uniform thicknesswithout the formation of nodules, trees and roughness which in priormethods had a tendency to form around the periphery of the object beingplated.

Still another object of this invention is to provide a device forelectroforming stampers comprising a backplate made of electricallyinsulating material, chemically inert to the electrolyte, a cathodeholder attached at one end to the back of said backplate, said cathodeholder having its other end adapted to electrically contact a negativebus bar, and means at the attached end to hold and make electricalcontact through said backplate with a metallized cathode surface of arecord to be plated, means attached to said backplate to provide astream of air bubbles through the plating solution and adjacent thesurface of the record to be plated, and a balespaced from said backplateand parallel thereto, and in front of the record `surface `being plated,said baffle being formed with a hole of smaller diameter than thediameter of the record being plated, whereby the electrodeposited metalis caused to distribute itself uniformly on the metallized cathodesurface, and permit appreciabie saving in copper.

Yet another object of this invention is to provide an economical methodof manufacture of stampers in which a minimum of equipment,

space and labor lis required. I

Other objects of this invention will in part be obvious and in parthereinafter pointed out.

The invention accordingly consists in the features of construction,combination of elements, arrangement of parts, and method steps whichwill be exemplified in the construction hereinafter described, and ofwhich the scope of invention will be indicated in the following claims.

In the accompanying drawings in which are shown illustrative.embodiments of this invention,

Fig. 1 is a front elevation vieW of a preferred embodiment of theinvention;

Fig. 2 is a cross-sectional view taken along the line 2-2 of Fig. l; j

Fig. 3 is a top plan view of the embodiment shown in Fig. 1;

4 sarir to turn the shells down to a uniform thickness on a lathe, anexcessive number of cuts are required toV make the stamper of uniformthickness and this makes the process expensive'both from the standpointof labor and loss due to copper scrap. Furthermore, there is a tendencyfor the outer edges to be cold worked excessively in the cuttingoperation on the lathe, resulting in a hardening and embrittling actionon the outer surfaces and causing distortion and even cracking of thestamper when removed from the cutting lathe.

' present invention for producing stampers overcome vallucf .thesedisadvantages.

Referring now to the drawings, particularly Figs.v l', ZandS, for a morecomplete understand- Fig. 4 is a top plan viewofltwor-unitSrQi the'.

embodiment shown in Fig. 1, in a plating tank;

Fig. 5 is a cross-sectional view taken along the line 5 5 of Fig. 4;,

Fig. Gris-a view similar to Fig.' 1 showing another embodiment of theinvention;

Fig. '7` isav top` plan view-'of the embodiment shown in Fig. 6;. l

Fig. 8 is a crossesectional View taken along line 8-8 of Fig. 6; v

Fig. 9 is an enlarged.cross-sectional view of a portion ofaphonograph-record whose surface has been metallized; l

Fig. 10- is Aa view similar to tion of the electroormed stamperdeposited on the metallized surfaceand y Fig. 11 is--an-enl'argedcross-sectional view of a portion of they electroformedstamper depositedon the metallized surface of the record and -removed from the record.

In themanufacture ofphonograph records electricaltranscriptions therehas been a great needv for producing an electro-formed shell or stamperwhich has a smooth'- surface without treesor nodules, is hard and`springy- `without being brittle, and has-a well controlled and constantthickness from the periphery tothe center. Also, itV is desirable toproduce these stampers as rapidi-vas possible. l y

In the usual `methode-ofA producing electroformed'shells or stampers,the original recording disc which is made` of' Waxor aluminum' coatedwith a lm of cellulose acetate, on which lthe recording grooves arecut,- is first; metallized to i make the surface' electricallyconductive. The conventional methods used are' either to rappl-y a goldnlm-by sputtering or to form a silver mirror by spraying or immersiontank methods. This filmer mirror isnext strengthened byV applying apreplate at low current density to buiid upa shell having a thickness ofapproximately 0.0005.V to 0.001". The recordV disc is then plated at ahigher current vdensity tobuild up athiokness of approximatelyV 0.050Vof metal, usually copper. Obviously, it is desirableA to produce thesestamp-. ers as rapidlyV as `possible and with aminimum outlay ofequipment and space. Most of the methods in common use take vfrom 16--to 48 hours to electroformthe shell or stamper. Faster plating methodshave been devised by rotating, the cathode, providing-a systeml ofbaffles and. circulating the plating solution. These methodsA arecomparatively expensivefrom the. standpoint of initial equipment cost,excessive space and maintenance required. Also, in most of the methodsin common use` the. electroformed shellsV show` a variation in thicknessofcopper, or other metal, of as much as- 0.050" from the center to thevoutside edge. In view of.' theV factk that itis neces- Fig. 9 showingapori and me of the invention.. i0 designates the plating deviceembodying the invention for electroform- 'ing' stampe'rs or dies used inthe manufacture of phonograph records and electrical transcriptions. Theplating devicel lil. comprises a rectangular support or backplate ilwhich may be made of a plate of chemically and electrically resistantmaterial such as Bakelite niicarta, or similar non-conducto-rofelectricity. Said backplate il comprises a frontV wall I2, a rear wallI3, a top edge. I4 and a bottom edge l5. Backplate Il, is further formedwith substantially 45 beveled edges l5 extending forwardly and. inwardlyfromV the rear wall i3 to the front Wall i2. At substantially the.center of backplate i l is a shallow discshaped recess il in WallV i2.Extending rearwardly from recess ll is a smaller disc-shaped recess i8,concentric with recess i7.. Extending rearwardly from recess [Si is aAround hole Isav communicating with the rear wall i3 of backplate ll forthe purpose hereinafter described.

To help prevent an excessive build-up of depositedmetal around theperiphery of the stamper to be formed and to prevent; treeing ofdeposited metal along the edges of the aluminum sheet to be described,there is attached toeach beveled edge l0 of backplate I l, by anysuitable means such as, screws i9, a rectangular sheet or baille 23..The baliies 20 aremade of the same composition as .baokplate Il arecoextensive with edges- IE andextend forwardly and inwardly of saidbackplate VI l.

`Flush withthe lower edge l5 and on theV front wall i2 of backplate H isa rectangular spacer bar 2l of rectangular cross-section and ofchemically and electrically inert material similar Vto said backplate ll. Said spacer bar 2l is attached to backplate ll by means of screws 23or any other `suitable means. The triangular shaped holes 2 la formedbetween the ends of the spacer bar and cailles 20 are for the purpose ofpermitting drainage-of electrolyte When device iii is removed from theplatingy bath.

In order to permit faster plating of the record by use of high. currentdensities with this invention, strong agitation of the plating solutionis provided byv a steady; stream of air bubbles through the solution andover the surface of the record to-be plated. To this end, there isprovideda member 2li.; Member 2S. may be made of the same composition asbackplate i! and comprises a rear wall 25 contacting the front wall ofspacer bar 2i and extending beyond the side edges thereof, a lowerhorizontal edge Z ilush with the lower llorizontal edge of spacer bar2l, a front wall 21 parallely to rear wall 25, and an upper Wall 28sloping downwardly and rearwardly at an' angle of substantially 45 fromfront' Wall Z'itoireargwall 2,5.l Walls 28. and 25 The devices andmethods of theV meet in a straight line which is substantially at thelevel of the upper horizontal edge of spacer bar 2I, or slightly abovethis level. Member 24 may be secured to spacer bar 2I by the screws 23or any other suitable means. The side edges 29 of member 24 are beveledin the same manner as side edges I6 of backplate II, and form planesurfaces therewith which contact the inner surfaces of baiiies 20 andterminate short of the forward edges of said baffles 2li. Member 24 isfurther formed with a plurality of vertical through openings 30 parallelto front wall 21 and communicating with the upper wall 28 and the loweredge 26.

Satisfactory results have been obtained in plating large record surfaceswhen the through openings 30 were ile in diameter and spaced about fromeach other.

In contact with the lower horizontal edge 26 of member 24, is the uppersurface of a rectangular bar 3|, of rectangular cross-section and of thesaine thickness and composition as member 24. Bar 3I which protrudesslightly from both sides 29 of member 24 is secured to member 24 byscrews 32 or any other suitable means. Bar 3| is further formed in itsupper surface with a vertical groove 33, which communicates with thethrough openings 36 of member 24, and which terminates short of the endsof said bar 3I. A round through passage 34 communicates with groove 33and one end surface of bar 3l. Inserted into the through passage 34 andextending beyond the end surface of bar 2I is a chemically andelectrically inert tube 35 for the purpose hereinafter described.

Electrical contact must be made between the negative terminal of asource of direct current, and the cathode or surface to be plated. Tothis end there is provided a heavy contact holder 36. Contact holder 36comprises a bar of metal, preferably copper, of rectangularcross-section, having a vertical portion 31 extending upwardly alongrear wall I3 from a point just below the center of backplate II to apoint above the upper edge I4 of backplate II. Extending from the upperend of vertical portion 31 and making an angle of about 135 therewith isa smaller rearwardly and upwardly inclined portion 38. Portion 38 isformed with a through opening 39 at its center for the purpose to behereinafter described. Extending from the upper end of portion 38 in adownwardly and rearwardly direction, making an angle of 90 therewith isa portion 40. It will now be seen that portions 3S and 40 form ahook-like structure adapted to engage a cathode bar of squarecross-section for an electrical connection. Vertical portion 31 isfurther formed with a round hole 4I spaced from its lower extremity, andin register with hole I8a in backplate II.

By means of wing nut 61 the whole assembly is held rigid so that thevertical stream of air bubbles rises parallel to the surface of therecord, agitating the solution in contact therewith but not actuallymaking contact with the record surface.

To connect contact holder 36 with the record surface to be plated thereis provided a rod 42, externally threaded at both ends, snugly insertedinto holes 4I and I8a. The forward flat end of rod 42 is flush withfront wall I2 of backplate` I I. The rear flat end of rod 42 projectsbeyond vertical portion 31 of contact holder 36 and is se. Cured theretoby-nut 4,3 in threaded engagement with rod 42. An internally threadeddisc-like metal insert 44, having a iiat front surface flush with frontwall I2 of backplate I I and adapted to snugly t into recesses I1 and I8of backplate I I, is threadedly engaged with the front external threadsof rod 42. Rod 42 is further formed with an axially threaded opening 45in its front end to receive a headed screw 46 for the purposehereinafter described.

To prevent the formation of nodules, trees and roughness around theedges of the record to be plated, particularly when high currentdensities are used, there is provided a rectangular metallic sheet 41,preferably of aluminum, which lies at against front wall I2 of backplateI I, and in contact with the front flat surface of insert 44. Aluminumsheets of between .005" to 11s have been found to produce satisfactoryresults. The bottom edge of sheet 41 rests on the upper edge of thespacer bar 2| and covers substantially the entire front Avvall I2 ofbackplate II, terminating just short of the sides and top thereof. Sheet41 is formed with an opening 48 at its center to register with opening45 in rod 42 and through which screw 46 passes. A metal washer 49 may beplaced against the head of screw 46. The record 5t to be plated isinterposed between the washer 43 and sheet 41 with the screw 46 passingthrough the hole 5I in the record 56. The icord surface to be plated isthe front surface All of the metal parts through which the platingcurrent will flow are preferably made of copper, with the exception ofsheet 41 which may be of aluminum, to provide a good conductor for theelectric current. All the metal parts, with the exceptions of thesurface to be plated and sheet 41 which come in contact with the platingsolution or electrolyte in the plating tank should be painted or coatedwith a chemically and electrically inert material in order to preventchemi cal and electrical reactions with the electrolyte.

It will now be understood that an electrical connection is made betweenthe metallized cathode surface 52 of record 50 and contact bar 36through washer 49, screw 46, sheet 41, insert 44, rod 42, nut 43 andvertical portion 31 of contact bar 36. Portions of the cellulose acetatefilm on record 5i?, near the center hole 5I may be scraped away toexpose a metal base to insure a good electrical contact between washer49 and sheet 41 when screw 46 is tightened.

For a better understanding of the plating process, reference is madeparticularly to Figs. 4 and 5 in which 53 designates a plating tank orcontainer. Tank 53 is filled to capacity with the usual plating solutionor electrolyte 54 which may be a solution of copper sulphate andsulfuric acid if, for instance, the stamper is to be made of copper.While stampers may be made of other metals, as for example nickel, theprocess of making copper stampers by this invention will be describedfor purposes of illustration. Two plating devices IE) are shown withintank 53 to illustrate the compactness and simplicity possible in thismethod of plating.

The anodes 62 may be placed as closely to the cathode surface as ispracticable which by virtue of the construction is about 2". There areseveral advantages accruing to this close spacing. One importantadvantage is the low solution IR drop with its resultant saving inelectrical power. .Another advantage is to be seen in the eifect of theair stream in agitating the solution in proximity to the anode surfacethus reducing anode 7. polarization andA any tendency towardsludge-forillatifh TanlcSS comprises asubstantially square bottom: wall55, parallel side walls 55, a iront-.iwan lV and a rear wall 5t.Extending outwardly from the upper liorizc'ntalledees of side walls 58;front wall 51 and rearwall B'lis `a squarenorizom tal flange 59. Restingon electrioallinsulatn blocks 59a on. flange :itV andparallel to sidewalls 5S are two metal anode bars 6c each. equally spaced from 'sidewallV 5c' or tank 53. Anous barsA till-` may be: offromdf or squarecross-'section and are preferably madeloiccpper. touact asr socalconductors of electricity'. `suspencllecl from each anodebar 60 by meansof hooks 61| aretwo ieee tangular copper bars 62 which are the sourcesof metal-used'oif plating' thestalil'pr'. .Ailde bls 60 arel'ctlicall-yconnected ta Gommoni al'l terminal 633s' at 64'f0`1 the' ulD'oSevofSlliaplyillg source of direct current 'to the plating solution 54j.

Midway between. anode bars Eil andi parallel thereto are two adjacentcathode bars E5 which act assupportsfor the plating! devices E9. Cathodebars r55 maybe of square cross-section so that they may rest on theiredgesl on flange 59| Extending upwardly and outwardly from each cathodebarde at its midpoint is a threaded shank 66. Platingrdev'lce- Hi! ishung on cathode bar E5 so that shanki` protrudes through open* ing 39 ofcathode holder 35. Wing nut iii is thenv screwedvcn shankt to make goodelectrical contact between the cathode holder 35 and the cathode bar 85.Cathode bars 65 are connected to a common cathoderterminal SS as at GQfor 'connection toj the negative terminal of a direct currentsupply.

A chemically inert flexible rubber tube ill is connected to tube 35 inmember 3i for the purposeV of supplying air under pressure from an aircompressor blower' through groove $3, openings te and over'themetallized cathode surface 52 of theA record 5o during the platingprocess.

To make a copperstamper of the metallized VcathodeV surface vili of therecord tii, a sourceV of direct current is' applied across anodeterminal E3- and cathode terminal 681. A copper pre-spiate atv alowcurrent density oi' about 25 amps/su. it. is formed on the metallizcdcathode surface until the thickness of the copper plate is oiapproximately 039005" to 0.001. noted that during the entire platingprocess copper will also be deposited on the aluminum sheet 4f?which-.extends beyond the periphery of record 59, and which iselectrically connected to the negative source of direct current.

Air under pressure is next introduced through tube 752 and flows throughpassage 34, groove 33, openings Sil and over the metallized surface 52being plated. The air uniformly,T agita/tes the plating solution alongthe whole plating surface. By varying the air pressure in tube 'lll anydegree of agitation of .the plating solution, from mildto extremelyviolent, may be produced. By using strong agitation comparatively highcurrent densities can be used and thus permit rapid elec-'-trodeposition to take place. Because of this uniform agitation overtheface of the nletallized cathode surface YE52 the metal electrodepositedis srhooth, uniform and of excellent physical characteristics for recordstampers.

The aluminum sheet lll' serves the functionv of preventing excessive`current density around the periphery of record 50. This is accomplishedby extending the metalliz'ed cathode surface 52 on to plate 4l andVcausing thecopper to plate onto Itl will be bothfaluininum sheet IH andmetallized cathode surface 52. The het euect come assembly of theplating device iii is to provide. very uniform current distribution overthe whole metallised cathode surface 521er the record 50 with.theresuit-.that the thickness'- oi 'the electro'ionned shell Ol* .stall f'h'lthe' c'iltel" to. the plphlfy vis suistltialiy' 'llllffilL dlth'drmre',the' tllde ency for nodules trees and roughness to'` occur over thesurface beingplated andparticularly amandine periphery of the recordsil, prac tically eliminated. Thisy smoothness and uni.- oimity isv adecided advantage sincaas pre-vlously pointed out, a single trimming outa lathe of a' fewthousandths is all that is required to produce asatisfactory iinished stariiper ready forv use. .in electroforming theVcoincer shell or stamper current densities asf highas 2G() ampsl/ sql.ft. 'may be employed with an -air pressure of about 3 lbsuntil a stampershell of 0.050 is formed. Exceilent results have been achieved lnbuilding up the requisite thickness of a stamper in from 6to l() hoursoythis method.

The barde-s 2li and inclined wall 28 of mem--i ber" 2d of plating deviceIl] serve the function of preventing the current from concentrating'along the edges of the nietalli'zed cathode surface 52 and the edges ofsheet 41 thus eliminating any tendency toward the formation of treesland nodules which, as is well known inthe art, are wasteful of metal andelectrical energy, partieularly when heavy electroplates are built up'.

In Figs. 6, 7 and 8 is shown ar'lotherv embodiment of a plating device"lill similar to thel platf ing device if! shown in Figs'. l, 2 and 3',except for the arrangement of the baffles and the' elimination of theVmetal sheet 571' behind the metal-e lined cathode surface 5'2 of therecord 5G to be plated. v'il'ie plating device Hf] comprises a rec*-tangular p1ismaticsha`ped support or backplate iii of the samey platematerial as backpla'te il'. Said back-platelll further comprises a frontwall H2, a' rear Wall H3; a top edge IM, a bote tom edge H5 and sideedges Ht; At substantially the center oi backplate iii are the sameconcentric disceshaped recesses il' and lii'ancl hole ma, as are formedin nackplate A system of baffles is attached to backplate for thepurpose of directing theA electrodeposited metal uniformly o n thestamper to be'formcd and thereby prevent the formation of trees andnodules which usually form around the periphery of the stamper. To this'end there are provided a pair of rectangular spacer plates H9, par'-allel to each other, and each adjacent and coextensive with side edgesH6 of backplate lll'. Plates H9 are of the same material as backplateill, are perpendicular to front wall H2 o1" said backplate Hl andattached thereto by any suitable means. Attached to the front edges ofplates H9 by any suitable means is a rectangular Vbaille 20 parallel .tobaclzplateA Ill, of the same chemically` and electrically inertmaterial, and coextensve therewith. Balile |26 is formed with a largeround hole 12M concentric with disc'- shaped recesses Ii and i3, andhole 18a. Hole Ia is of slightly smaller diameter than the metallizedcathode surface 52 of the record to be plated'. f

Flush with the Ylower edgev IIE and on the front wall ||2 of packplate|.|'1f is a rectaneailar` spacer bar |21. Spacer bar |2| isv attached tobackplatc by meansof screws |23 or any other suitable means.Tneparallelside edges of'spacer par :2| terminate shortfof theinnersurfaces' of 9, plates I l 9 thereby forming a rectangular `throughopening |2|a for the purpose of permitting drainage of electrolyte whendevice |111 is 4removed from theplating bath. Spacer bar |2.| is made ofthe 'same material `as backpla-te To provide strong agitation of theplating solution by supplying a steady stream of air bubbles through theplating solution and adjacent the cathode surface to be plated, there isprovided a prismatic-shaped member |24 similar in function to member 24of plating device .10. Member |24 is made of the same materialasbackplate and comprises a rear wall |25 contacting the front wall ofspacer bar |2| and extending beyond the side edges thereof, a lowerhorizontal wall 25 flush with the lower horizontal edge of spacer bar|2|, a front wall |21 parallel to rear wall |25,

vand an upper wall |28 parallel to lower wall |26 and flush with theupper horizontal edge of spacer bar |21. The parallel side edges ofmember |24 contact the inner surfaces of plates H9. Member |22 isfurther formed with a plurality of vertical through openings |30parallel to front wall |21 and communicating with upper walll|28 andlower wall |25, similar to openings 3in `member 24 of plating devicelil. Member |24 may be secured to spacer bar |2| by screws |23 or anyothe suitable means.

In contact with and suitably attached to fthe lower horizontal wall |26of member |24 and the lower edges of plates I9 is the upper surface-of arectangular prismatic bar `3|. Bar 3| has the same construction andfunction in relation to member IZLlof plating device Il@ as it has inrelation to member 24 of plating device I0. Interposed between andsuitably attached to baille |2 and the upper portion of front wall I 21is a spacer bar |3|.

It will now be understood that 'a continuous stream of air underpressure from an air compressor can be introduced through tube 35, pas-vlsage 34, groove 33, openings |39 and over the metallized cathodesurface 52 of record 59 during the plating process. i

In plating device the rear surface of record U is placed flush againstfront wall H2 ofbackplate Il and secured thereto in the same manner asrecord 5t is secured to plating device EL It will be noted, however,that in plating device IIB there is no metal plate interposed betweenthe back of the record 50 and the front wall ||2 of the backplatelii. l

It will now be understood that an electrical connection is made betweenthe metallized cathode surface of record 5!) and contact bar 36 throughwasher 49, screw 5.6, insert 44, rod 42 and nut 43.

Plating device lli! can now be suspended into tank 53 in the same manneras plating device l0 and metallized cathode surface 52 of record 5i) cannow be plated to electroform a stamper as previously described. It willbe noted however that in plating device Ill the entire cathode surfaceplated is the metallized cathode surface 52 of record 55. In platingdevice l, the entire cathode surface plated is the metallized cathodesurface 52 of record 5B and the .portions of metal sheet 31 that extendbeyond .the periphery of record. 55.

Baiie |23@ functions to prevent an excess of metal from depositingaround the periphery of the stamper. This is accomplished by divertingthe metal ions in the plating solutionfrom the periphery of the recordbecause in travelling from the anode bars 52 to the metallized cathodesurface "52, said ions must pass through hole |2|la which has asmallerdiameter thansaid metallized cathode surface.

Referringnow particularly to Figs. 9, 10 and 11, therecordor electricaltranscription to be plated is` represented by numeral 50. Record 50comprises a metal base 5|a, usually of aluminum, a bottom side 5 lb,usually of a plastic material such ascellulose acetate, and a top side5to also of a similar plastic material. Sound recordings are cut intothe top side 5|c, for instance, by a recording machine well known in theart. These recordings are in the form of grooves 5|d. In order to make astamper of these grooves 5|d the entire surface 5| c is metallized by avery thin coating of metal, usually in the form of a silver mirror ormetallized cathode surface 52.

In the plating process the stamper 52a usually of copper,` is depositedon the metallized cathode surface 52. When stamper 52a is of therequired thickness it is pried loose from the record surface 5Ic.Stamper 52a, with the thin metallized surface 52 adhered to itnowcontains an impression of the sound recording made on the record and iscapable of functioning as a die to stamp out similar recordings. Byusing the above plating devices and methods a stamper of substantiallyuniform thickness, an excellent stamping characteristic, is produced.

If desired a metallic sheet like sheet 41 may be employed in theapparatus shown in Figures 6, 7 and 8, interposed between the record 50and the front wall 2 of backplate While the above specication hasdescribed the invention with relation to a metallized matrix surface ofa plastic or non-metallic record or matrix, it is understood that theinventive method may be applied to a metal matrix surface also.

It will thus be seen that there are provided devices and processes inwhich the several ob jects of this invention are achieved and which arewell adapted to meet the conditions of practical use. l Y

As various possible embodiments might be made of the above invention,and as various changes might be made in the above embodiment set forth,it is understood that all matter herein set forth or shownV in theaccompanying drawings is to be interpretedv as illustrative and not in alimiting sense.

I claim:

l. A device for plating the front metallized surface of a'phonographrecord comprising a backplate, a cathode holder attached to the back ofsaid backplate, said cathode holder having means on one end toelectrically contact a negative bus bar of a source of direct current,and means at the other end to make electrical contact through saidbackplate with said metallized .surface of said` phonograph record,means in the front of said backplate to hold the rear surface of saidphonograph 'record in contact with the front surface of said backplate,and means near the bote tom of. said backplate to direct a stream of airbubbles adjacent to said metallized surface, and a baliie supported by'said holder and disposed in front of and spaced from said record andhaving aholeopposed to said record, saidbackplate and haliiebeing madeof electrical insulating material resistantto plating solution.

2. A device for plating the front metallized surface of a phonographrecord comprising a backplate, a cathode holder attached to the back ofsaid backplate, said cathode holder having means on one end toelectrically contact a negative bus bar of a source of direct current,and means at scrapes 111 the other end to vmake'electricalcontactthrough said backplate with said metallized surface of saidphonograph record, means in the front of said backplate to hold .therear'surface'of said phonograph record lin contact with the frontsurface of vsaid backplate, means near-the bottom of said backplate todirect a stream of air bubbles adjacent to said metallized surface, saidlast means comprising a member `attached tothe bach'-Y plate and havinga plurality of vertical through openings parallel to each other, andabar attached to .the underside of said member, formed with alongitudinal groove in its upper surface and communicating with saidthrough openings and with a through ,passage at one Vend of .said bar toreceive air from an air compressor, a bale attached to said member anddisposedin front of and spaced from said backplate and having an openingopposed to said record, sa'idfbackplate member, bar and baille beingmade of electrical insulatingr material :resistant Vto platingsolutions.

3. A device Afor plating 'the frontfmetallized'surface oi a lphonographrecord comprising :a hackplate, a cathode holder attached "to the backof said backplate, isaid cathode holder Ehaving means on one end toelectrically contact a'negative'bus bar-of a source of direct current,and ,means .aat the other end to make electrical vContact through saidbackplate with said :metallized surface of said phonograph record, meansin the vfront Yof said backplate to hold the Vrear surface of saidphonograph record ineen-tact with the front surface of said backplate,means near the Ebcl'oln of said backplate to direct a Vstream 'of airbubbles adjacent to said metallized surface, and ay baille attached tosaid backplate and located in frontof and spaced from `said metallizedsurface. said baile being formed with a circular holeof smaller diameterthan the diameter of saidimetallized surface, said backplate and baillebeing madeof electric insulating materialresistant to plating solution.

4. A plating device for electroformingstampers forphonograph recordscomprising a backplatefa cathode holder attachedto the back ofsaid-backplate, said `cathode holder having means "on'one end to makevelectrical conta-ct with a negative'bus bar, and means .onthe other endto .malte-zelectri cal contact through said backplate with a metalliaedcathode surface of phonograph record, means in "thefront of saidback-plate to hold said phonograph record against said backplatefandlabaie attached to `said front of said backplate, said baille being spacedfrom said backplate `and metallized `cathode surface, and formed with 4acircular hole having a smaller diameter than said metall-ized cathodesurface of said phonograph record andl concentric therewith, wherebylthe plating current is prevented from concentrating around theperiphery and the forma-tionlof noda ules, trees and roughness preventedaround the periphery of said .metallized-cath'ode surface, saidbackplate and baffle A'being :m'ad'efof electric inV sulating materialresistant to plating solutions. and means to supply airunderjpressure:between the metallized surface and baille.

5. A vdevice for plating the front metall-izedsur face lof aphonographic record in a plating tank provided with a negative bus bar'of a vsource of I2 directlcurre'nt, saiddevioe comprising aunit whichmay be .-'hungon the @bus bar to project down into plating vsolution inthev tank, said unit comprising a cathodeholder having means at itsupperend for removable attachment to said negative bus bar, means onsai-dholder to support a phonograph 4vrecord having a front metallizedsurface and to-make electrical contact with the metallized surface ofsaid phonograph record, a bale plate of electric resistant materialsupported by said holder bar in spaced relation in front of thephonograph record, said Vbaille being formed with an'openingin opposedrelation to the record, and means supported by said holder to directspaced streamsof .air bubbles adjacent said metallized surface and.between the record and baile, said unit being removable as a whole fromthe bus bar.

6. 'The device of claim 5 in combination with a backing `plate ofelectrical resisting material, supported on the holder and against whichthe back of the recordcontacts.

7. A `portable unitary device -for plating the front `rr'i'et'al-lizedsurface of a phonograph record, comprising a cathode .holder having ahook at its upper end `from which it may be hung on the nega'tivebusibar `of a plating tank, a record having a front Ymetallized surface,means on the holder bar toysupport said record on a horizontal axis andltomake electrical contact with the front metallized surface .of saidrecord, a bale of electrical Tesistantmaterial supported by said holderbar and disposed in front of the record in spaced relation thereto-and-being formed with an opening substantially coextensi-ve with themetallized surface of .said record whereby current in the plating tankisdirected 4through the opening to saidmetallizedfsurface, means supportedby said holder bar and located between the lower end of the baffle andthe record to direct upwardly, streams'of nir bubbles to agitate theplating solution in the r'tank, said device 'being removable from thetank as. a unit by unhooking the holder bar from t-hebns bar.

8. The device of claim 'l' in combination with a. backing plate ofelectrical resistant `material contacting the back of the record andsupported on said holder.

References cited in the me of uns patent :UNITED STATES PATENTS OTHERV'REFERENCES A Principles of .Electroplating andElectroforminggbyWilliam'Blum and George B. Hogaboom, 3rd edition, 1949,pages 270 and 271.

1. A DEVICE FOR PLATING TH EFRONT METALLIZED SURFACE OF A PHONOGRAPHRECORD COMPRISING A BACKPLATE, A CATHODE HOLDER ATTACHED TO THE BACK OFSAID BACKPLATE, SAID CATHODE HOLDER HAVING MEANS ON ONE END TOELECTRICALLY CONTACT A NEGATIVE BUS BAR OF A SOURCE OF DIRECT CURRENT,AND MEANS AT THE OTHER END TO MAKE ELECTRICAL CONTACT THROUGH SAIDBACKPLATE WITH SAID METALLIZED SURFACE OF SAID PHONOGRAPH RECORD, MEANSIN THE FRONT OF SAID BACKPLATE TO HOLD THE REAR SURFACE OF SAIDPHONOGRAPH RECORD IN CONTACT WITH THE FRONT SURFACE OF SAID BACKPLATE,AND MEANS NEAR THE BOT-